1. Field of the Invention
The present invention relates to the field of the administration of a medicinal preparation, preferably (i) in a relatively small amount and (ii) for relatively long periods of time.
More precisely, it relates to an administration method and device which can be used mainly in the field of arterial, venous or subcutaneous perfusion and also in the field of the percutaneous administration of active principles, where the said active principles, placed in contact with the skin, pass through the skin and enter the organism.
By virtue of this method and this device, the strictly necessary amount of medicinal preparation is administered to the patient, especially by perfusion.
2. DESCRIPTION OF THE RELATED ART
It is known that two apparatuses have hitherto been used for perfusion in hospitals, namely the drip and the automatic syringe.
The drip, which is often used because it is very economic, gives a very random flow, it being possible for the volume of perfusion liquid administered to vary by .+-.150% since it is adjusted manually. The drip has several other disadvantages, i.e. especially (i) the introduction of a large volume of liquid (generally isotonic) into the patient's systemic circulation, which is not always desirable, in particular if the patient is suffering from renal or other disorders which prevent or limit urination, and (ii) immobilazation of the patient.
On the other hand, the automatic syringe, when it is actually working, is theoretically very efficient as regards the precision of the flow; it delivers a uniform flow and only introduces the strictly required amount of perfusion liquid into the systemic circulation. Unfortunately, the automatic syringe has numerous disadvantages: it involves immobilizing the patient, is relatively very expensive, frequently breaks down and requires highly qualified technical staff to make the required flow adjustments (not always easy).
It is also known that, as far as the drip technique is concerned, devices for the continuous perfusion of ambulant patients have been proposed. French patent documents 2,447,198, 2,447,199 and 2,499,857, in particular, have disclosed a device comprising a pliable and flexible container of solution, a transfer orifice connected to the said container and a flexible tube running from the said orifice to the patient's catheter, which is provided with a breakable element.
U.S. Pat. No. 4,298,000 has disclosed a perfusion device in which a capillary for regulating the flow of the medicinal preparation to be administered is located downstream of the reservoir containing the said preparation.
The said document neither describes nor suggests the use, upstream of the said reservoir, of (i) a hydraulic accumulator of the type comprising a flexible membrane fixed in a leaktight manner around the said device, or (ii) a capillary regulating the admission of the hydraulic fluid for pushing the perfusion preparation towards its administration site.
Also, U.S. Pat. No. 4,201,207 has disclosed another perfusion device, in which the preparation to be administered is accommodated in a rubber envelope (or bladder), which is compressed and discharges into a distributing element via a capillary needle. The said document neither describes nor suggests the use of a hydraulic accumulator acting upstream of the reservoir containing the perfusion preparation, via a capillary regulating the admission of the hydraulic fluid driving a piston for pushing the said preparation towards its administration site.
Finally, the daily newspaper "Le Monde" of Wednesday 22 Apr. 1987 (published on 21 Apr. 1987) disclosed, on page 23, that a perfusion device for chemotherapeutic chemotherapeutic treatment had been recommended. The said device, the principle of which is based on the retraction of a latex membrane, comprises a large syringe equipped with a balloon-shaped reservoir of 70 ml capacity, and a flow controller apparently provided with a filter membrane of 5 .mu.m mesh. Via the said filter membrane, the said device delivers 2 ml/h of medicinal solution for venous, arterial or subcutaneous administration by means of a catheter. Now, the retraction of a latex membrane alone does not ensure uniformity of the flow of the medicinal preparation to be distributed.